The present invention generally relates to electro-optic devices, and more particularly relates to electrochromic devices used in architectural windows or vehicle rearview mirrors.
Electrochromic elements are used in a variety of applications including light shutters, variable attenuating optical filters, and architectural and vehicle windows. The most common application of electrochromic elements is in rearview mirror assemblies used in vehicles. Such electrochromic rearview mirrors are controlled to vary the reflectivity of the mirror in response to rearward and forward aimed light sensors so as to reduce the glare of headlamps in the image reflected to the driver's eyes.
FIG. 1A shows an exploded view of a portion of a rearview mirror subassembly 5 as used in a typical exterior rearview mirror assembly. Subassembly 5 includes an electrochromic mirror element 10, a bezel 50, and a carrier plate 70 (FIG. 1B). The subassembly may further include gaskets 60 and 62, which are placed on either side of electrochromic mirror element 10, which are provided to form a secondary seal around the periphery of the mirror element 10. As best shown in FIG. 1B, electrochromic element 10 includes a front transparent element 12, typically formed of glass, and having a front surface 12a and a rear surface 12b. Electrochromic element 10 further includes a rear element 14, which is spaced slightly apart from element 12. A seal 16 is formed between elements 12 and 14 about their periphery so as to define a sealed chamber therebetween in which an electrochromic medium is provided. Elements 12 and 14 preferably have electrically conductive layers on the surfaces facing the chamber such that an electrical potential may be applied across the electrochromic medium. These electrodes would be electrically isolated from one another and separately coupled to a power source by means of first and second buss connectors 34a and 34b. To facilitate connection of buss connectors 34a and 34b, elements 12 and 14 are typically vertically offset so that one buss connector may be secured along a bottom edge of one of the elements and another buss connector may be secured to the top edge of the other element. The buss connectors 34a and 34b are typically spring clips similar to those disclosed in commonly-assigned U.S. Pat. No. 6,064,509 so as to ensure that they remain physically and electrically coupled to the electrode layers on the inward-facing surfaces of elements 12 and 14. Once the electrochromic element 10 has been manufactured and buss clips 34a and 34b attached, the mirror subassembly 5 may then be assembled. As shown in FIGS. 1A and 1B, bezel 50 includes a front lip 51, which extends over a portion of the front surface 12a of front element 12. Typically, front lip 51 extends over a sufficient portion of front surface 12a to obscure a person's view of seal 16 and protect seal 16 from possible UV degradation. As apparent from FIG. 1B, the width D1 of front lip 51 of bezel 50 is dependent upon a number of factors including the distance D2 of offset of elements 12 and 14. Also, the extent to which buss connector clip 34a and 34b extend beyond the peripheral edges of elements 12 and 14 may require a wider bezel. Typical prior art bezels have a front lip with a width D1 of 5 mm or more.
Prior to inserting electrochromic mirror element 10 in bezel 50, an optional front gasket 60 may be provided behind front lip 51 so as to be pressed between front surface 12a of front element 12 and the inner surface of front lip 51 of bezel 50. Mirror element 10 is then placed in bezel 50 and an optional rear gasket 62 may be provided along the periphery of the back surface of element 14 or the bezel/mirror interface area may be filled or potted with a sealing material like urethane, silicone, or epoxy. A carrier plate 70, which is typically formed of an engineering grade rigid plastic or a similar material as used for bezel 50, is then pressed against the rear surface of element 14 with gasket 62 compressed therebetween. A plurality of tabs 52 may be formed inside of the bezel such that carrier plate 70 is snapped in place so as to secure mirror element 10 within the bezel.
Carrier plate 70 is typically used to mount the mirror subassembly within an exterior mirror housing. More specifically, an optional motor (not shown) may also be mounted within the mirror housing and mechanically coupled to carrier plate 70 for enabling remote adjustment of the position of the mirror subassembly within the housing.
While the above-described structure is readily manufacturable, styling concerns have arisen with respect to the width of the front lip of the bezel of an electrochromic mirror subassembly. Specifically, due to the need to accommodate the buss clips, the positional offset of elements 12 and 14, and to obscure the view of the seal, the width of the front lip of the bezel is typically wider than that of any bezel used on non-dimming (non-electrochromic) mirrors. In fact, bezels are often not used on non-dimming mirrors. In some vehicles, only the exterior mirror on the driver's side is electrochromic, while the passenger side mirror is non-dimming. Thus, there exists the need for an improved electrochromic exterior mirror subassembly that has a reduced bezel front width or that does not include a front bezel at all.